Molecular and structural impacts of fungal depolymerization of corn stover to reduce pretreatment severity

Abstract

The recalcitrance of lignocellulosic feedstocks to depolymerization is a significant barrier for renewable energy conversion approaches that require monomeric carbohydrates as inputs to conversion. This study assesses whether feedstock supply chain operations can be transformed into targeted pretreatments. Corn stover was inoculated with lignin degrading filamentous fungi (Phanerochaete chrysosporium), and then stored in aerated bioreactors designed to mimic storage conditions in large-scale storage piles to determine if fungal pretreatment enhanced lignin degradation. Composition changes resulting from P. chrysosporium treatment included hemicellulose and lignin degradation. Pyrolysis GC×GC/MS indicates that the cleavage of glycosidic bonds in hemicellulose resulted in sugar degradation products. Enhanced G and S lignol releases were observed. Dilute acid pretreatment and enzymatic hydrolysis indicated that lowering the reaction temperature to reduce pretreatment severity resulted in equivalent xylose release in unstored and fungal treated samples. These results suggest that this combined biological, thermochemical pretreatment can augment glycosidic bond cleavage and lignin degradation in lignocellulosic biorefineries.